Helicopter blade folding and locking mechanism

ABSTRACT

A power piston actuates a series of link members which are pivotally interconnected and which are also pivotally connected to the rotor hub and the blade so that actuation of the power piston will actuate said links to cause said blade to move to its folded position and to be locked in the folded position due to a link over-center condition.

United States Patent Ferris July 3, 1973 [5 HELICOPTER BLADE FOLDING AND3.356.155 l2/l967 Ferris 416/143 LOCKING MECHANISM 3,369,611 2/1968Vacca et al 4l6/l42 3,438,446 4/l969 Vacca et al 4l6/l43 [75] lnventor:Donald L. Ferris, Newtown, Conn. [73] Assignee: United AircraftCorporation, East primary EXaminer Eve,-ene powe".

Hartford Conn- Attorney-Vernon F. Hauschild [22] Filed: Nov. 2, 1971[2]] Appl. No.: 194,881 57 ABSTRACT A power piston actuates a series oflink members which (gill. are pivotany interconnected and which are alsopivot [58] Fi d 6/1 42 l ally connected to the rotor hub and the bladeso that e o 2 /7 actuation of the power piston will actuate said linksto cause said blade to move to its folded position and to ReferencesCited be locked in the folded position due to a link over- UNITED STATESPATENTS Vacca et a] 416/142 center condition.

14 Claims, 6 Drawing Figures PATENTEUJUL 3 I975 SHEEF 1 0F 4 ATTORNEYPATENTEDJUL 31m sum 2 0f 4 IIII| PAIENTEIIJIIL 3mm 3.743441 SHEET u 0? aANGLE IN RELATIONSHIP TO PLANE OF ROTOR (X) I CENTERLINE OF ROTORL v9FOLD PIN AXIS WITH ANGLES X8.Y

PLANE PERPENDICu- LAR TO ROTOR PLANE L'FEATHERING AXIS TO BLADE (UN OLDEI FEATI-IERINO AXIS EPLANE FOLD PIN OFFSET I ANGLE IN RELATIO (ONE sIDEOR THE OTHER 253 IQXEQ Q R OF FEATHERING AxIs) 0FOLD H65 f/ PATH OFBLADE WITH NO .ANGLE TO FEATHERING AXIS OR ROTOR PLANE z (ANGLE OF FOLD)/PATH OF BLADE WITH ANGLE Y IN RELATION- SHIP TO FEATHERING AXIS PLANEPATH OF BLADE WITH ANGLE Y IN RELATIONSHIP TO FEATHERING AXIS PLANE ANDANGLE X IN RELATIONSHIP FINAL VERTICAL BLADE To PLANE OF ROTORDISPLACEMENT (SAM E) HELICOPTER BLADE FOLDING AND LOCKING I MECHANISMBACKGROUND OF THE INVENTION 1. Field of the Invention Thisinventionrelates to the folding of helicopter blades and moreparticularly to the folding of helicopter blades wherein the blades arelocked both in their folded and in their unfolded positions and whereinthe folded blades so locked require no external force to maintain thefold lock.

2. Description of the Prior Art In the helicopter blade folding art,folding mechanism have been used in which gear sectors are actuated tocause blade folding and unfolding, and separate link sets serve to holdthe blade in the fully folded position. These gear mechanisms not onlyrequire intricate machining but must be adjusted for back-lash. Inaddition, the sliding surfaces of the gear faces must be kept lubricatedto reduce wear on these surfaces. Further, the separate links must beperiodically adjusted because of the wear on the sector gears.

Other types of blade fold mechanisms use complicated series of links andcams, most of which are located externally of the blade and hub and aretherefore vulnerable to breakage in use and by firearms, corrosiondamage besides being complicated in nature and are aerodynamicallyunsound.

SUMMARY OF THE INVENTION A primary object of this invention is toprovide an improved blade fold and lock mechanism in which the blade isboth folded and locked by a simple link mecha' nism.

In accordance with the present invention, the entire blade folding andlocking mechanism is located internally within the blade or hub so thatit is protected thereby from damage due to external forces.

In accordance with a further aspect of the present invention, the linksare of a selected length and orientation to fit the fold angle andover-center requirements, and best provide, within the limits ofpracticality, a maximum folding moment about the fold pin at the pointsof maximum blade resistance to folding and unfolding of the blades.

In accordance with still a further aspect of the present invention,apparatus is provided to control the degree of folding of the blade andto positively stop the power piston when the blade is in its fullyfolded condition.

In accordance with still a further aspect of the present invention, thefolding links go into over-center-relationship when the blade is in itsfullyfolded position and so remain when hydraulic power is removed fromthe power piston. I v

In accordance with still a further feature of the present invention, theblade is folded about a fold pin having an axis forming a selected anglewith the blade feathering axis and with the blade plane of rotation soas to safely and selectively control the path of the blade during thefolding operation and to selectively position the blade in the desiredfully folded position, while maintaining adequate clearance from theground, fuselage, and other blades during the folding operation.

Other objects and advantages of the present invention may be seen byreferring to the following description and claims, read in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of my bladefolding and lock mechanism in its rotor head environment, partiallybroken away to reveal the folding and locking mechanism in the bladeoperating or unfolded position.

FIG. 2 is a side view of my blade fold mechanism in the blade operativeor unfolded position, partially in cross section.

FIG. 3 is a plan view of my blade fold mechanism in the blade foldedposition.

FIG. 4 is a schematic representation of the blade fold pin and its axiswith respect to the blade feathering axis and the rotor plane ofrotation.

FIG. 5 is a graphic representation of blade fold motion for threeselected conditions.

FIG. 6 is a partial showing of my invention in a second type of rotorhead.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 wesee my blade fold mechanism in its helicopter rotor environment in itsblade unfolded or operating position. As best shown in these figures,helicopter rotor 10 comprises rotor hub 12 which is mounted for rotationabout axis of rotation 14 and helicopter blade 16, which is one of aseries of identical blades projecting from hub 12 for rotation therewithabout axis 14 so as to create lift. Blades 16 are mounted from hub 12 soas to be rotatable about feathering axis 18 through the action of pitchchange horn 20, which is controlled by conventional pitch change controlmechanism (not shown). Blade 16 is connected to hub 12 through foldhinge 15 and through sleeve 22, which generally envelops the blade foldand lock mechanism 30. There is one such mechanism 30 for each blade ofdifferent fold angle and both the blades and their blade fold and lockmechanism which may be identical, but not necessarily so due todifferent clearance problems around the aircraft.

Blade 16 is pivotally connected to fold hinge 15 through fold pin 17 topermit blade folding and to sleeve 22 and hence hub 14. As best shown inFIG. 4, the axis 19 of fold pin 17 forms a selected angle with respectto both the plane of the blade feathering axis 18 and the rotor plane ofrotation 21 so as to permit the blade tofollow a selected path duringthe folding and unfolding motion and to assume a selected position whenfully folded so as to avoid all obstacles, including the ground, thefuselage, and other blades, during the folding and unfolding motion andso as to nest selectively with the otherblades, fuselage, or the likewhen in the fully folded position The significance of the compound angleof axis 19 of fold pin 17 depicted in FIG. 4 is best understood byviewing FIG. Sin which line 51 represents the blade operational or zerodegree fold positions and line 53 represents the blade fully foldedposition. Line 55 represents the path of a blade when blade folding axis19 does not form an angle to the feathering axis plane or the rotorplane. The result of blade fold motion along line 55 would beinterference between the various blades during the blade folding andunfolding operation. Line 57 represents the path when a blade which hasselected angular relationship with the blade feathering axis plane onlyand not with'the plane of the rotor. While blades following path 57would not interfere with one another, the maximum downward verticaldisplacement of the blade, which would be encountered at the blade 90fold angle, would exceed the minimum required ground clearance andtherefore the blade would possibly strike the ground during bladefolding and unfolding operation. Line 59 is the path of blade fold whenthe angular relationship shown in FIG. 4 exists between the blade foldpin axis and both the rotor planeand the feathering axis plane. It willbe noted that blade path 59 provides increased ground clearance duringthe blade folding and unfolding operations and therefore avoids theblade striking the ground, however, the final vertical bladedisplacement is the same, and therefore the blade fully folded nestingposition is the same for blade paths 57 and 59.

While FIGS. 1-3 illustrate my blade fold and lock mechanism 30 in theenvironment of a particular rotor head, it should be noted that as bestshown in FIG. 6, my blade fold and lock mechanism 30 is also usable witha conventional sleeve and spindle rotor head of the type shown in US.Pat. No. 3,097,701, wherein the piston and crank or link mechanism wouldbe mounted within the spindle and rotation between the spindle andsleeve would be taken out by a selfaligning hearing at 52.

Still viewing FIGS. 1 and 2, we see that blade fold and lock mechanism30 includes linkage assembly 32, which is powered by powercylinder-piston arrangement 34, which includes piston member 36positioned within cylinder 38 and with provisions for either air orhydraulic fluid to be directed thereinto either through port 40 or port42 to actuate linkage mechanism 32. As best shown in FIG. 2, when theactuating fluid enters chamber 44 through port 42, piston 36 movesleftwardly to move linkage mechanism 32 to its blade fold position and,when actuating fluid enters chamber 46 through port 40, it moves piston36 to the right, to unfold the blade 16 and return it to its normaloperation position. Spacer 48 is positioned in cylinder 38 and is ofselected width W to serve as a positive stop for piston 36 when theblades are in their fully folded position. Spacers of selected width Wmay be used to vary piston 36 stroke.

Piston rod 50 connects through spherical clevis joint 52 to one end oflink member 54, while the other end of link 54 connects throughspherical clevis joint 56 to one of the three corners of triangular link58. A second corner of triangular link 58 is pivotally connected atpivot joint 60 to sleeve 22. Link 58 is connected at its third corner atpivot joint 62 to twin link members 64, which are pivotally connected attheir other ends at pivot connection 66 to fold bracket 70, which is, inturn, connected to fold hinge 15 through bolt members 73.

It will-be noted, as best shown in FIG. l, the joints 66, 62 and 60 forma triangle when the blade is in its operative, nonfolded position withthe interconnected pivot joint 62 closest to hub 12, and with one corner60 of the triangle connected to the hub, while the other corner 66 ofthe triangle is connected to the fold bracket 70 in turn to fold hinge land to blade 16.

When blade 16 is in its operating position shown in FIGS. 1 and 2,flanges 72 of sleeve 22 engage flanges 74 of fold hinge so that a singlelock pin 76 can pass through aligned apertures in these flanges to lockblade 16 and fold hinge 15 in its unfolded or operable FIGS. 1 and 2position. Pin 76 can be withdrawn from inner flanges of 72-74 by anyconventional mechanism such as conventional solenoid 79 to permit bladefolding. This is the first step in the blade folding operation.Thereafter, actuating fluid is caused to enter chamber 44 to move piston36 leftwardly and thereby cause piston rod 50 to move link 54leftwardly. As best shown in FIG. 1, this leftward movement of piston 36causes axis 86 to move along are or action line 88, thereby causing axis82 to move along action line 84, and axis 78 to move along action line80, while pivot joint 60 causes link 58 to pivot about pivot axis 90. Asthis motion continues, the link mechanism 32 passes through a positionin which pivot axes 78, 82 and 90 are in alignment. With these axes inalignment, the blade has folded slightly beyond its intended fullyfolded position. As this motion continues, links 58 and 64 assume theover-center condition shown in FIG. 3, thereby returning and lockingblade 16 in its fully folded position even when hydraulic fluid isremoved from piston-cylinder arrangement 34. Over-center spring 92,which extends between fold bracket and link 58 serves to retain links 58and 64 in their over-centered, locked position. Over-centering the linkstends to put a tension load on piston 36, reacted by spacer 48 whenblade wind forces is in the unfold direction. Fold links 58 and 64 movefrom the over-center condition to a straight line condition when bladewind force is in a fold direction. This provides tension on links 64 and50. Spring 92, being preloaded in tension, tends to return blade to itsovercenter condition when wind force in fold direction slackens.

It will accordingly be seen that links 58 and 64 coact, when powered bypower piston 34, to both fold and lock blade 16 in its folded positionwith respect to hub 12.

Link 58 is made triangular in shape so that the most effective momentarms of point 86 about axis 60, and

point 82 about axis may be achieved to overcome the blade folding loadsin their most severe fold angle condition. The added advantage is inproviding a smaller stroke of piston 36, reducing the required length ofthe sleeve, and reducing packaging requirements.

Shim 94, of selected thickness, may be positioned between fold bracket70 and the remainder of blade 16 so as to selectively control or adjustthe final angle to which link mechanism 32 causes blade 16 to fold withrespect to hub 12.

It will also be noted by viewing FIG. 1 that while the line of actionbetween link 54 and the pivot connections 90 and 78 of links 58 and 64are of selected dimension when the blade is in its FIG. I operative,unfolded position, this distance increases as the links folcl towardtheir FIG. 3 positions so as to provide the most effective momentpossible when the blade folding and unfolding loads are maximum duringthe folding and unfolding operation.

By viewing FIGS. 1 and 3, it will be seen that due to the motion of linkmechanism 30, when actuated by power piston-cylinder arrangement 34,blade 16 is actuated between its FIG. 1 operable position to its FIG. 3fully loaded position, having folded through a number of degreesrepresented by angle A. It will be obvious to those skilled in the artthat by control of the stroke of piston 36, the length of the variouslinks in link mechanism 30, and shimming at 94, the angle through whichthe blade is caused to fold may be varied.

It will therefore be seen that my construction teaches a linkagemechanism which is power actuated to not only cause a helicopter bladeto fold with respect to the hub a selected angular amount but also to belocked in the precise desired position when fully folded.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

I claim:

1. A helicopter rotor having:

A. a hub,

B. a blade pivotally connected to said hub in blade fold relationship,

C. means to fold said blade with respect to said hub and to lock saidblade in a folded position includ- 1. two pivotally connected links ofselected length and orientation so that the link free ends form atriangle with their interconnected ends so oriented that theirinterconnected ends are on the hub side of a line passing between thelink free ends,

2. means pivotally connecting the free end of one of said links to saidhub,

3. means pivotally connecting the free end of the other of said links tothe foldable blade, and

4. power means connected to force said pivotally interconnected linkends to the line extending between the pivot connections of said linksto said hub and to said blade to thereby cause said blade to fold withrespect to said hub, and to a position therebeyond so that said linksare in over-center relationship to lock said blade in said foldedcondition.

2. A helicopter rotor according to claim 1 wherein said power meansincludes a. powered cylinder-piston mechanism connected to said bladefold means so that motion of said piston within said cylinder causespivot motion of said links.

3. A helicopter rotor according to claim 2 and including means tocontrol the stroke of said piston and hence the angle of folding of saidblade.

4. A rotor according to claim 3 and including a link member pivotallyconnected to said piston at one of its ends and pivotally connected tosaid link interconnected ends at its other end.

5. A rotor according to claim 1 and including means operativelyconnected to said blade fold means to vary the angle through which saidblade is folded.

6. A rotor according to claim 1 wherein said blade is pivotallyconnected to said hub by means of a blade fold pin whose axis isselectively oriented so as to form a preselected angle in relation tothe blade feathering axis to control the path of folded'motion of theblade in its finally fully folded position and which also forms aselected angle relative to the rotor plane of rotation to provideadequate ground clearance for the blade during the folding motion.

7. A rotor according to claim 6 wherein the distance between the linesof force between said power means and said link pivot connections tosaid hub and said blade increase as the blade is so powered to a foldedposition so as to create maximum moments at the location of maximumblade resistance to folding.

8. A rotor according to claim 1 wherein one of said links issubstantially triangular in shape with one corner thereof pivotallyconnected to the other link, with a second corner thereof pivotallyconnected to the hub or blade and with the third corner thereofpivotally connected to the power means.

9. A rotor according to claim 1 and including an over-center springconnected between said blade and one of said links to restrain saidlinks in the over-center relationship.

10. A rotor according to claim 1 and including single pin means to locksaid blade to said hub when the blade is in its operable position.

11. A rotor according to claim 2 including means to control the strokeof said piston, and means to vary the angle of blade fold for thecontrolled piston stroke.

12. A helicopter rotor including:

A. a hub,

B. a blade connected to said hub for folding motion with respectthereto,

C. blade folding and locking mechanism including:

1. a first link member of substantially triangular shape pivotallyconnected to said hub at one of its comers,

2. a second link member pivotally connected to said blade at one of itsends and pivotally connected to the second corner of said first link andbeing of selected length and orientation so that the pivotalinterconnection between the first and second links is on the hub side ofa line extending between the pivotal connection between the first linkand the hub and the second link and the blade,

3. a third link member pivotally connected to the third corner of saidfirst link member,

4. a power cylinder-piston arrangement having:

a. a cylinder,

b. a piston mounted in said cylinder for reciprocation with respectthereto,

c. a connecting rod connected to said piston and pivotally connected atits opposite end to the other end of said third link,

so that as said piston moves within said power pistoncylinderarrangement, said third link will cause the pivot interconnectionbetween said first and second links to move into alignment with thepivot interconnection between said first link and said hub and saidsecond link and said blade so as to cause the blade to fold with respectto the hub to a position beyond its normal fully folded position, andthen to cause said pivotal interconnection between said first and secondlinks to move to a positiontherebeyond to establish an overfor a pistonstroke so controlled.

1. A helicopter rotor having: A. a hub, B. a blade pivotally connectedto said hub in blade fold relationship, C. means to fold said blade withrespect to said hub and to lock said blade in a folded positionincluding:
 1. two pivotally connected links of selected length andorientation so that the link free ends form a triangle with theirinterconnected ends so oriented that their interconnected ends are onthe hub side of a line passing between the link free ends,
 2. meanspivotally connecting the free end of one of said links to said hub, 3.means pivotally connecting the free end of the other of said links tothe foldable blade, and
 4. power means connected to force said pivotallyinterconnected link ends to the line extending between the pivotconnections of said links to said hub and to said blade to thereby causesaid blade to fold with respect to said hub, and to a positiontherebeyond so that said links are in over-center relationship to locksaid blade in said folded condition.
 2. means pivotally connecting thefree end of one of said links to said hub,
 2. a second link memberpivotally connected to said blade at one of its ends and pivotallyconnected to the second corner of said first link and being of selectedlength and orientation so that the pivotal interconnection between thefirst and second links is on the hub side of a line extending betweenthe pivotal connection between the first link and the hub and the secondlink and the blade,
 2. A helicopter rotor according to claim 1 whereinsaid power means includes a powered cylinder-piston mechanism connectedto said blade fold means so that motion of said piston within saidcylinder causes pivot motion of said links.
 3. a third link memberpivotally connected to the third corner of said first link member,
 3. Ahelicopter rotor according to claim 2 and including meaNs to control thestroke of said piston and hence the angle of folding of said blade. 3.means pivotally connecting the free end of the other of said links tothe foldable blade, and
 4. a power cylinder-piston arrangement having:a. a cylinder, b. a piston mounted in said cylinder for reciprocationwith respect thereto, c. a connecting rod connected to said piston andpivotally connected at its opposite end to the other end of said thirdlink, so that as said piston moves within said power piston-cylinderarrangement, said third link will cause the pivot interconnectionbetween said first and second links to move into alignment with thepivot interconnection between said first link and said hub and saidsecond link and said blade so as to cause the blade to fold with respectto the hub to a position beyond its normal fully folded position, andthen to cause said pivotal interconnection between said first and secondlinks to move to a position therebeyond to establish an over-centerrelationship therebetween to return the blade to its fully foldedposition and to so lock the blade so positioned.
 4. power meansconnected to force said pivotally interconnected link ends to the lineextending between the pivot connections of said links to said hub and tosaid blade to thereby cause said blade to fold with respect to said hub,and to a position therebeyond so that said links are in over-centerrelationship to lock said blade in said folded condition.
 4. A rotoraccording to claim 3 and including a link member pivotally connected tosaid piston at one of its ends and pivotally connected to said linkinterconnected ends at its other end.
 5. A rotor according to claim 1and including means operatively connected to said blade fold means tovary the angle through which said blade is folded.
 6. A rotor accordingto claim 1 wherein said blade is pivotally connected to said hub bymeans of a blade fold pin whose axis is selectively oriented so as toform a preselected angle in relation to the blade feathering axis tocontrol the path of folded motion of the blade in its finally fullyfolded position and which also forms a selected angle relative to therotor plane of rotation to provide adequate ground clearance for theblade during the folding motion.
 7. A rotor according to claim 6 whereinthe distance between the lines of force between said power means andsaid link pivot connections to said hub and said blade increase as theblade is so powered to a folded position so as to create maximum momentsat the location of maximum blade resistance to folding.
 8. A rotoraccording to claim 1 wherein one of said links is substantiallytriangular in shape with one corner thereof pivotally connected to theother link, with a second corner thereof pivotally connected to the hubor blade and with the third corner thereof pivotally connected to thepower means.
 9. A rotor according to claim 1 and including anover-center spring connected between said blade and one of said links torestrain said links in the over-center relationship.
 10. A rotoraccording to claim 1 and including single pin means to lock said bladeto said hub when the blade is in its operable position.
 11. A rotoraccording to claim 2 including means to control the stroke of saidpiston, and means to vary the angle of blade fold for the controlledpiston stroke.
 12. A helicopter rotor including: A. a hub, B. a bladeconnected to said hub for folding motion with respect thereto, C. bladefolding and locking mechanism including:
 13. Apparatus according toclaim 12 and including means to control the stroke of the piston. 14.Apparatus according to claim 13 and including means to vary the angularfolding motion of said blade for a piston stroke so controlled.